Amyloidosis is characterized by the deposition of a homogenous eosinophilic material in the parenchyma and around blood vessels. Amyloidosis was originally divided into two types: primary amyloidosis in association with plasma cell disorders, which occurs as an idiopathic or familial disease, and secondary amyloidosis, found in conjunction with another inflammatory disease (e.g., juvenile rheumatoid arthritis, familial Mediterranean fever [FMF], chronic pulmonary disease, or osteomyelitis). A classification of different types of amyloidoses is summarized in Table 435.1.

In primary or amyloid-containing immunoglobulin light-chain amyloidosis (see Table 435.1), the principal sites of involvement are the skin and gastrointestinal tract. The patient may present with macroglossia, carpal tunnel syndrome or arthritis, congestive heart failure, malabsorption, or gastrointestinal bleeding. In secondary or amyloid A (AA) amyloidosis (see Table 435.1), the patient develops hepatomegaly, splenomegaly, and nephrotic syndrome. Secondary amyloidosis is a rare occurrence in children, but it is seen in association with Hodgkin disease or renal carcinoma, in addition to the inflammatory diseases mentioned previously. In young adults, it increases in frequency in chronic suppurative conditions, with the infectious complications of intravenous drug use, and in diseases such as leprosy or malaria. Amyloidosis has also been described in endocrine organs, in association with diabetes and thyroid disease and as localized cutaneous deposits (see Table 435.1).